Generic data fields used to add publicly accessible properties to
RenderContent.FieldDictionary. These should be created by calling a
FieldDictaionary.Add() method on a Render content object. These are
allocated after the RenderContent object's C++ object is created and
added to the underlying C++ objects content dictionary, who ever
allocates a field is responsible for deleting it so these objects clean
up the C++ pointers when they are disposed of.

Dictionary containing RenderContent data fields, add fields to this
dictionary in your derived RenderContent classes constructor. Get field
values using the TryGet[data type]() methods and set them using the Set()
method.